MAXM17543EVKIT datasheet(2/10 Pages) MAXIM

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Evaluates: MAXM17543 in 3.3V

Output-Voltage Application

MAXM17543 3.3V Output

Evaluation Kit

Quick Start

Recommended Equipment

● MAXM17543 EV kit

● 4.5V to 42V DC power supply (VIN)

● Dummy load capable of sinking 2.5A

● Digital voltmeter (DVM)

● 100MHz dual-trace oscilloscope

Procedure

The EV kit is fully assembled and tested. Follow the steps

below to verify board operation.

Caution: Do not turn on

the power supply until all connections are completed.

1) Set the power supply at a voltage between 4.5V and

42V. Disable the power supply.

2) Connect the positive and negative terminals of the

power supply to IN and PGND PCB pads, respectively.

3) Connect the positive and negative terminals of the

2.5A load to OUT and PGND2 PCB pads, respectively,

and set the load to 0A.

4) Connect the DVM across the OUT PCB pad and the

PGND2 PCB pad.

5) Verify that no shunts are installed across pin 1-2 on

jumper JU1 to enable UVLO (see Table 1 for details).

6) Verify that a shunt is installed across JU3 to disable

the external synchronization (see Table 3 for details).

7) Verify that a shunt is installed across JU2 to enable

PWM mode (see Table 2 for details).

8) Enable the input power supply.

9) Verify the DVM displays 3.3V.

10) Increase the load up to 2.5A to verify the DVM

continues displaying 3.3V.

Detailed Description of Hardware

The EV kit is a proven circuit to demonstrate the

high-voltage, high-efficiency, and compact solution-size

of the synchronous step-down DC-DC power module.

The output voltage is preset for 3.3V to operate from

4.5V to 42V and provides up to 2.5A load current.

The optimal frequency is set at 500kHz to maximize

efficiency and minimize component size. The EV kit

includes JU1 to enable/disable UVLO of the device, JU2

to configure in PWM, PFM, or DCM mode to improve

light-load efficiency, and JU3 to enable/disable external

clock synchronization (SYNC). The RESET PCB pad is

also available for monitoring output-voltage regulation

to enable/disable the application circuit of the load. The

electrolytic capacitor (C8) is required only when the VIN

power supply is situated far from the MAXM17543 circuit.

When R4 is open, the device switches at 500kHz switching

frequency. On the bottom layer, additional footprints of

optional components are included to allow for easy board

modification for different input/output configurations.

Soft-Start Input (SS)

The device utilizes an adjustable soft-start function to

limit inrush current during startup. The soft-start time is

programmed by the value of the external capacitor from

SS to GND (C1). The selected output capacitance (CSEL)

and the output voltage (VOUT) determine the minimum

value of C1, as shown by the following equation:

SEL

OUT

C1 28 10

−

≥×

where C1 is in nF and CSEL is in µF

The soft-start time (tSS) is calculated by the equation below:

C1/ 5.55

where tSS is in ms and C1 is in nF.

Programmable Undervoltage-Lockout (UVLO)

The EV kit offers an adjustable-input, undervoltage-lock-

out level by resistor-dividers connected between the IN,

EN/UVLO, and GND pins. For normal operation, a shunt

should not be installed across pins 1-2 on JU1 to enable

the output through an internal pullup 3.3MΩ resistor from

the EN/UVLO pin to the IN pin. To disable the output,

install the shunt across pins 1-2 on JU1 to pull EN/UVLO

pin to GND. See Table 1 for JU1 jumper setting details.

The EV kit also provides an optional R3 PCB footprint

to program a UVLO threshold voltage at which an input-

voltage level device turns on. The R3 resistor can be

calculated by the following equation:

INU

4009.5

1.215)

−

where VINU is the input voltage at which the device is

required to turn on, and R3 unit is in kΩ.

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